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Re: [RFC][PATCH -tip 7/9] tracing: kprobe-tracer plugin supports arguments
- From: Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>
- To: Masami Hiramatsu <mhiramat at redhat dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, systemtap-ml <systemtap at sources dot redhat dot com>, LKML <linux-kernel at vger dot kernel dot org>
- Date: Fri, 20 Mar 2009 13:49:14 +0530
- Subject: Re: [RFC][PATCH -tip 7/9] tracing: kprobe-tracer plugin supports arguments
- References: <49C2B4D0.8030904@redhat.com>
- Reply-to: ananth at in dot ibm dot com
On Thu, Mar 19, 2009 at 05:10:40PM -0400, Masami Hiramatsu wrote:
> +#if defined(__i386__)
> +#define REGPARMS 3
> +static unsigned long fetch_argument(struct pt_regs *regs, void *data)
> +{
> + unsigned long n = (unsigned long)data;
> + if (n > REGPARMS) {
> + /*
> + * The typical case: arg n is on the stack.
> + * stack[0] = return address
> + */
> + return fetch_stack(regs, (void *)(n - REGPARMS));
> + } else {
> + switch (n) {
> + case 1: return regs->ax;
> + case 2: return regs->dx;
> + case 3: return regs->cx;
> + }
> + return 0;
> + }
> +}
> +#elif define(__x86_64__)
#elif defined(__x86_64__)
> +#define REGPARMS 6
> +static unsigned long fetch_argument(struct pt_regs *regs, void *data)
> +{
> + unsigned long n = (unsigned long)data;
> + if (n > REGPARMS) {
> + /*
> + * The typical case: arg n is on the stack.
> + * stack[0] = return address
> + */
> + return fetch_stack(regs, (void *)(n - REGPARMS));
> + } else {
> + switch (n) {
> + case 1: return regs->di;
> + case 2: return regs->si;
> + case 3: return regs->dx;
> + case 4: return regs->cx;
> + case 5: return regs->r8;
> + case 6: return regs->r9;
> + }
> + return 0;
> + }
> +}
> +#else
> +static unsigned long fetch_argument(struct pt_regs *regs, void *data)
> +{
> + return fetch_stack(regs, data);
> +}
> +#endif
As mentioned in another email, if we can generalize something similar to
syscall_get_arguments, this can be made to work for many !x86 archs.
AFAICS the calling conventions mandated by the ABI are followed at
syscall time, isn't it?
Ananth